Add support for the Sofle Pico keyboard

[fishjord]

Description

Adds Sofle Pico support. This sofle variant was designed specifically for the RP2040 and supports addtional features not found in the legacy Sofle variants.

QMK Pull Request

QMK PR: qmk/qmk_firmware#25750

VIA Keymap Pull Request

VIA userspace PR: the-via/qmk_userspace_via#122

Checklist

• The VIA support for this keyboard is MERGED in QMK master already (MANDATORY)
• VIA keymap is MERGED in VIA userspace master already (MANDATORY)
• The VIA definition follows the guide here: https://caniusevia.com/docs/layouts
• I have a V3 JSON version for this keyboard definition.(MANDATORY)
• I have formatted the JSON file to have consistent formatting with the rest of the repository.
• I have tested this keyboard definition using VIA's "Design" tab.
• I have tested this keyboard definition with firmware on a device.
• I have assigned alpha keys and modifier keys with the correct colors.
• The Vendor ID is not 0xFEED